Silica particles silane functionalization

The stationary phase (sorbent) is the most important part of an SPE cartridge. The most common SPE phases are bonded silica-based materials. Various silanes are used to attach functional groups to the accessible areas of the silica particle. The functional group determines the identity and chromatographic characteristics of the phase. In addition, several nonsilica-based phases are also available. Samples that are dirty, complex, or highly concentrated will require larger amounts of phase for sufficient sample cleanup. 

This method of silanation, which uses organic solvent without the addition of water, is suitable for highly reactive silane derivatives, such as chlorosilanes, aminosilanes, and methoxysilanes. This procedure will not work for ethoxysilanes, as these compounds are not reactive enough without prior hydrolysis to create the silanol. This method is convenient to use for silica particle modification and for the functionalization of metallic nanoparticles having the requisite—OH groups present (see Chapter 14, Section 5). 

Surface functionalization of silica particles or fluorescent silica particles typically is done using functional alkyl silanes. The process may be used to add a reactive group to the surface of the particles for spontaneous coupling to biomolecules or it may be used to add the appropriate nucleophilic group to the surface, such as an amine or a carboxylate. Silane modification chemistry is discussed in more detail in Chapter 13. 

Markowitz et al. developed a different approach, again in an attempt to overcome some of the inherent difficulties that arise when imprinted bulk materials are used as catalysts [82], Here, the authors used a template-directed method to imprint an a-chymotrypsin TSA at the surface of silica nanoparticles, prepared with a number of organically modified silanes as functional monomers. Silica particle formation was performed in a microemulsion, where a mixture of a non-ionic surfactant and... 

Fig. 17 Dependence of the grafted amount of PVFA (yc) on the initial volume fraction of VFA used to graft on vinyl silane-functionalized silica particles (xVfa)...

Covalent immobilization of (photo) initiator groups on the support surface (see Scheme 4c) had been done on silica particles using a silanization with a conjugate of an azo-initiator [79,80]. MIP functionalization with L-phenylalanine anilide as template and MAA/EDMA along with UV-initiation [79] was feasible without significant polymerization in the bulk of the reaction mixture, and the synthesized composite materials were superior compared to conventional MIP particles. Most remarkably, the enantioseparation performance (capacity and... 

The surface of silica particles has many exposed silanol —OH groups which are known to imdergo facile reaction with silanes contained —Si(OR), —Si(Cl), and —Si(H) units, and with acyl or sul-fonyl acid chloride functional groups [31,32]. Thus, preparation of the desired derivatized silica particles was easily accomplished by refluxing sihca in a nonhydroxyhc solvent with excess ti receptor reagents such as 3,5- or 2,4-dinitrobenzoyl or dinitrobenzenesulfonyl chloride. This... 

Functionalization of the polymer has been widely employed in binary nanocomposites to improve the polymer/filler interactions and thus maximize the load transfer. Functionalization also serves to enhance the compatibility between the two components of polymer blend. Many grades of functionalized polymers are now available, including maleated grades and silane-grafted polymers. Examples of functionalized matrices studied in ternary nanocomposite studies include PP-g-MA [41], PP-g-VTEOS [27] and examples of functionalized elastomers include SEBS-g-MA [8,49,65], EPR-g-MA [19,44,65], POE-g-MA [75], and EPDM- -MA [64]. It is also important to note that only nonpolar matrices and elastomers require functionalization, as opposed to polar polymers like PA6, which present natural interactions with polar fillers such as silica particles and clay platelets. 

Micropacked columns are available with most of the bonded-phase packings used in HPLC. Porous and non-porous silica particles are optionally functionalized with covalently ound silanes or other strongly adsorbed materials. ALkyl-bonded silicas produce separations, generally based on solute volatility, but with the potential for selectivity differences based on interaction with silanol groups. Underivatized silica is popular for petroleum separations of aliphatic and aromatic hydrocarbons. Silver-ion-containing silica columns are selective for olefin separations. Huoroalkyl-bonded... 

Inorganic-organic hybrid silica was prepared via co-condensation of tetraethoxy- or tetramethoxysilane (TEOS or TMOS) and aminoalkoxysilane with appropriate amounts of ethanol (or methanol), water, and ammonia. The amine functional groups in the silica were converted to N-diazeniumdiolate NO donors via exposure to high pressures of NO (5 atm) under basic conditions. Control over both the structure and concentration of the silane precursors (i.e., tetraalkoxy-and aminoalkoxysilanes) and specific synthetic conditions allowed for the preparation of NO donor silica particles of widely varying sizes (20-500 nm), NO payloads (50-1,780 nmol/mg), maximum amounts of NO released (10-5,500 ppb/mg), half-lives (0.1-12 h), and NO release durations (up to 30 h)... 

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